Fair Value - Changes in Level 3 Financial Assets (Details) - Recurring - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 129	$ 111
Net realized and unrealized capital losses:
Included in earnings	(10)	(9)
Included in other comprehensive income (loss)	1	(9)
Purchases	41	95
Sales	(3)	(30)
Settlements		0
Gross transfers out of level 3	(50)	(29)
Ending balance	108	129
Commercial mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0
Net realized and unrealized capital losses:
Included in earnings	0
Included in other comprehensive income (loss)	0
Purchases	13
Sales	0
Gross transfers out of level 3	(13)
Ending balance	0	0
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	5
Net realized and unrealized capital losses:
Included in earnings		0
Included in other comprehensive income (loss)		0
Purchases		0
Sales		(5)
Settlements		0
Gross transfers out of level 3		0
Ending balance		0
U.S. corporate securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	61	38
Net realized and unrealized capital losses:
Included in earnings	(8)	(8)
Included in other comprehensive income (loss)	1	(5)
Purchases	5	36
Sales	(1)	0
Settlements		0
Gross transfers out of level 3	(29)	0
Ending balance	29	61
Foreign securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	8	10
Net realized and unrealized capital losses:
Included in earnings	0	0
Included in other comprehensive income (loss)	0	(2)
Purchases	0	0
Sales	0	0
Settlements		0
Gross transfers out of level 3	(8)	0
Ending balance	0	8
Other asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	3
Net realized and unrealized capital losses:
Included in earnings
Included in other comprehensive income (loss)		(2)
Purchases		30
Sales		(2)
Settlements		0
Gross transfers out of level 3		(29)
Ending balance		0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	60	55
Net realized and unrealized capital losses:
Included in earnings	(2)	(1)
Included in other comprehensive income (loss)	0	0
Purchases	23	29
Sales	(2)	(23)
Settlements		0
Gross transfers out of level 3	0	0
Ending balance	$ 79	$ 60